Apparatus for roll-forming an automotive bumper

ABSTRACT

A bumper bar for vehicles formed from rolled sheet steel having a closed tubular profile designed to have a high impact resistance, high strength-to-weight ratio, and a low cost of manufacture. The bar is preferably swept along its longitudinal axis to create a curvature consistent with modern automotive design.

This is a division of application Ser. No. 07/499,100, filed Mar. 26,1990.

AREA OF INVENTION

This invention relates to automotive bumper bars, and more specificallya roll-formed tubular bumper made of high strength sheet steel of lessthan 0.100 inch thickness with a high impact resistance, low weight, andrelatively low cost of manufacture.

BACKGROUND OF THE INVENTION

Automotive bumpers are subject to a variety of design requirements dueto consumer demands, government regulation, and the competitiveness ofthe industry. Bumpers must maintain a high level of strength and damageresistance to meet consumer expectation and government regulationconcerning low speed vehicular impact. However, a bumper must also be oflow weight to minimize vehicular dead weight which reduces gas mileageand increases suspension requirements. Also, bumpers must have a lowmanufacturing cost and high dimensional consistency given thecompetitiveness of the industry. Thus, high strength-to-weight ratiosand ease of manufacture are critical to the success of present bumpersystems.

These requirements are further complicated by the present aerodynamicdesign trends which call for a high degree of sweep across the front ofautomobiles, such sweep also contributing to the strength of the bumperand its spring-back characteristics.

A variety of designs and methods have been tried to improve bumpers.Many have used new metallic materials (such as aluminum or heattreatable steel alloys) and engineering resins (such as urethanes andelastomers) with varying degrees of success However, many of these newmaterials suffer from availability and cost problems as well as specialprocessing problems. In addition, where combinations of materials areused, assembly time is increased. Further, the automotive industrycontinues to demand even higher strength-to-weight ratios.

A conventional bumper has a C-shape formed of relatively low strengthand thick steel. Many of such C-shaped bumpers are roll-formed and someare formed with a sweep at the end of the roll-forming operation bypassing them over mandrels.

A problem of the traditional, predominant, "C" section bumper is thesudden collapse experienced during deflection when the horizontalflanges give way. The sudden failure makes it more difficult to properlytrigger the inflation of air bags which are intended to cushionpassengers from secondary impacts during a vehicle crash.

Lastly, bumper attachment methods have become more critical as bumperstrengths increase. Forces of impact are larger and transferred moredirectly.

Thus, it is an intention of this invention to greatly improve strengthand reduce weight over present bumper systems while utilizing availablematerials in a reliable and cost-efficient process of manufacture.

It is a further intention of this invention to provide a bumper whichprovides its strength and impact resistance over an extended deflectioncycle without experiencing the sudden failure experienced by theprevalent traditional "C" section bumpers.

It is also an intention of this invention to provide a method ofmanufacture allowing a high degree of sweep along the longitudinallength of the bumper, thus allowing for designs which meet the highlyaerodynamic designs called for by modern trends and also producing astronger bumper with improved spring-back characteristics.

It is also an intention of this invention to provide a unique attachmentmeans which will meet the requirements of such a high strength bumper.

SUMMARY OF THE INVENTION

The present invention provides an automotive bumper bar and the methodof making such bumper made of high strength steel and roll-formed into atubular cross section. The bumper may be made from a variety of highstrength steels of varying thickness and rolled into a variety oftubular cross-sectional shapes.

The invention solves the aforementioned problems by roll-forming aclosed tubular cross section from high strength sheet steel of at least60 KSI and 0.100 inches maximum thickness. By forming a closed section,the strength of the bar is greatly increased. This allows weightreduction by use of a reduced material thickness. The closed design alsoimproves deflection curves by avoiding the sudden collapse experiencedby traditional "C" section bumpers as the flanges give way.

A narrower but important aspect of this invention is the formation of asweep during the roll-forming process. This sweep allows for manufactureof a bumper which will satisfy modern aerodynamic designs and alsoincrease the strength of the bumper and improve its spring-backcharacteristics.

A still narrower aspect of this invention allows for formation of anattachment surface capable of withstanding the force created by animpact upon the bumper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a roll-formed bumper of the invention;

FIG. 2 is a plan view of the roll-formed bumper of the invention with asweep;

FIG. 2A is an enlarged portion of a center portion of the plan view ofFIG. 2;

FIG. 3 is a cross-sectional view of the bumper in FIG. 2 and also shownin FIG. 4 taken along the plane III--III;

FIG. 4 is a schematic view of the roll form apparatus of this inventionand for practicing the process of this invention;

FIG. 5 is a sketch illustrating the method employed to measure sweep;

FIG. 6 is a perspective, cross-sectional view taken along the planeVI--VI of FIG. 4;

FIG. 7 is a cross-sectional view taken along the plane VII--VII of FIG.6;

FIG. 8 is a perspective, cross-sectional view taken along the planeVIII--VIII of FIG. 4;

FIG. 9 is a cross-sectional view taken along the plane IX--IX of FIG. 4;

FIG. 10 is a cut-away, schematic view of a side of the sweeping meansshowing the sweeping mandrels and anchoring rod;

FIG. 11 is a frontal view of the sweeping station disclosing themandrels which form the curvature in the bumper;

FIG. 12 is a schematic of a section of the roll-form apparatusillustrating the position of a mandrel at the last two rollers;

FIG. 13 is a view of the back side of a modified end of the bumper;

FIG. 14 is a plan view of the modified end of the bumper illustratingthe attachment of the same to a support on a vehicle; and

FIG. 15 is a partial, perspective view of the end of the bumper asdisclosed in FIGS. 13 and 14.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The bumper bar of this invention is best disclosed in FIGS. 1, 2, 2A and3, which discloses the bumper bar 1 having a front side 2, rear side 3,top side 4, and bottom side 5. Front side 2 includes an indentation 6having an upper ledge 7, lower ledge 8, and central portion 9. Rear side3 also includes indentation 10 composed of an upper edge 11 and loweredge 12. Indentations 6 and 10 are provided for two reasons.Indentations 6 and 10 contribute to and thus increase the strength ofthe bumper 1 and also provides the unique function of advancing orcontributing to the movement of the bumper over the sweep formingmandrel as will be explained hereinafter. Bumper bar 1 is constructed ofa sheet of high strength steel roll-formed to cause its edges to abutone another. The edges are permanently induction welded as disclosed bythe welded seam 13. The bumper is roll-formed by apparatus schematicallydepicted in FIG. 4 using traditional components of a roll-formingapparatus 20 uniquely modified as will be disclosed hereinafter toproduce an unusually high radius sweep as disclosed in FIG. 2.

Sweep, as used in the automotive industry, is the term utilized todescribe the curvature of the bumper. Measurements of sweep may bederived from charts such as disclosed below which include themeasurements of the distance from a vertical plane "P" located at theforwardmost point of the bumper and perpendicular to the longitudinalaxis of the car to various points along the bumper as disclosed in FIG.5.

    ______________________________________                                        Point Location vs. Sweep                                                      *SWEEP  RA-     **A    B    C    D    E    F                                  NUMBER  DIUS    (30)   (25) (20) (15) (10) (5)  C/L                           ______________________________________                                         0      0       0      0    0    0    0    0    0                              1      3600     .125   .087                                                                               .056                                                                               .031                                                                              .014 .004 0                              5      720      .625   .434                                                                               .278                                                                               .156                                                                              .070 .017 0                             10      360     1.250  .868  .555                                                                               .312                                                                              .139 .035 0                             20      181     2.500  1.733                                                                              1.107                                                                               .622                                                                              .276 .069 0                             40      92.50   5.000  3.443                                                                              2.188                                                                              1.224                                                                              .542 .135 0                             60      63.75   7.500  5.107                                                                              3.219                                                                              1.790                                                                              .789 .196 0                             ______________________________________                                         *All digits are in inches and are rounded to 3 digits unless otherwise        noted.                                                                        **The letters indicate points located at 5.0" increments from the center      line C/L as illustrated in FIG. 5. For example, point F is 5.0" from C/L,     point E is 10.0" from C/L, point D is 15.0" from C/L, . . . and point A i     30.0" from C/L.                                                          

Referring to the above chart and FIG. 5, the relative position ofvarious points can easily be determined. For example, in a #5 sweep(i.e. a curvature having a 720" radius), point A which is 30.0" fromlongitudinal centerline (C/L) of the car is 0.625" (the distance "d")rearward of the front plant "P" of the bumper. Similarly, in a #60 sweep(i.e. curvature having a 63.75" radius), point A is 7.500" (the distance"d") rearward of the front plane "P" of the bumper. The sweep on presentday bumpers has been extremely limited by the structural design of suchbumpers and the methods and apparatus of manufacturing the same. As aresult, the sweep generally has been below 30 sweep. Bumpers constructedin accordance with this invention have fallen within the range of 30-60sweep which was unheard of in the automotive industry.

Although bumper bar 1 is formed from a sheet of high strength steel, thespecific grade and type of high strength steel may vary within a rangeof parameters depending upon the specific application in question. Thisrange includes two specific parameters which in accordance with narrowaspects of this invention are important to the invention; specifically,the tensile strength generally measured in units of KSI (thousand poundsof force per square inch) and thickness generally measured in thethousandths of an inch or in millimeters (mm). In accordance with themore narrow aspects of this invention, the KSI range presently availablesteel is from 60 to 120 although higher strength steels might be used asthey may become available, it being understood therefore that the KSIrange must be at least 60 KSI. The thickness range is from 0.048 to0.100 inches, it also being understood that if higher strength steelsabove 120 KSI become available, the thickness may be even less than0.048 inches. In any event, to obtain the maximum advantage of theinvention, the thickness must be less than 0.100 inches.

Bumpers have been successfully formed by this invention from steelordered pursuant to ASTM A606-85 and ASTM A715-87 designations morespecifically discussed hereinafter. However, experience suggests thatthe materials need not be limited to these two materials. Use of evenhigher strength materials such as Martinsite (an ultra high strengthmaterial of 150-200 KSI) is contemplated. It should be noted that "ASTM"is a commonly recognized abbreviation for the American Society forTesting and Materials, and the suffix "85" means that the standard wasre-approved in 1985 by the ASTM committee having jurisdiction over thisstandard. Details on ASTM specifications and designations are availablethrough the ASTM society, as is widely known in the industry. Therefore,only cursory information is included hereinafter.

"ASTM A606-85" is an ASTM designation calling for a high-strength, lowalloy, rolled steel with improved atmospheric corrosion resistance and atensile strength of up to approximately 70 KSI. The material is intendedfor structural use where savings in weight and added durability areimportant. Various "types" may be ordered such as "Type 4", forinstance, which has four times the corrosion resistance of plain carbonsteel. Various ordering information is required such as type of rolling(hot or cold rolled), dimensions (height, width, thickness), specialrequirement, and etc. The chemical composition is varied by the steelmanufacturer to meet specific strength and formability requirements ofthe user.

"ASTM A715-87" is an ASTM designation calling for a high-strength, lowalloy, rolled steel with improved formability over ASTM A606 materials.The steel is killed to form fine grain steel and includes variouscombinations of special micro-alloying elements such as columbium,titanium, vanadium, zirconium, and other elements. ASTM A715 offersimproved formability as well as improved weldability, and may includetensile strengths of up to 90 KSI.

The inventor has also utilized AISI 050WK and AISI 120XF materialssuccessfully. "AISI" is a commonly recognized abbreviation in theindustry for the American Iron and Steel Institute. AISI specificationsare typically cross-referenced to the most similar ASTM designation, butcontain a slightly different classification scheme. For example, AISI050WK refers to ASTM A606-85 with the "050" standing for minimum tensileyield strength (in KSI), the "W" for weatherability, and the "K" for thefact that the steel is killed. AISI 120XF has no ASTM reference atpresent, but is similar to ASTM A715-87 in that AISI 120XF has a highminimum yield strength (120 KSI minimum), is low alloy ("X"), and killedplus inclusion control ("F"). AISI 120XF may or may not be supplied as aG60 minimum spangle galvanized sheet.

As noted, within the above ranges the specific type and grade of highstrength steel may vary depending on the application. The materialthickness, chemical composition, and tensile strength all affectcross-sectional formability and the ability to form a sweep. Theinventor has successfully formed steel having a 0.072" thickness and atensile strength of 80-120 KSI to a #40 sweep from the above materials.Steel having a 0.072" thickness and a tensile strength of 80 KSI hassuccessfully been formed to a #60 sweep. However, by experience, we havediscovered that in the use of a steel having manganese, the maximummanganese content of 1.2 percent (1.2%) is preferred in the process ofthis invention in that a steel with greater manganese content resultedin a problem of "shelving". Shelving is a problem which may beexperienced in roll-forming wherein the steel will separate intolaminate "shelves" due to the high shear and stress of forming. Shelvingis undesirable since it results in material separation and greatlyreduces a bumper bar's strength and reliability.

FIG. 4 discloses a schematic of the unique apparatus for forming thebumper bar 1 of this invention and thus illustrates the process inproducing the bumper bar. In FIG. 4 reference numeral 20 designates theoverall apparatus which starting from the left side of the figurediscloses the steel roll holder 21 which rotatably supports the steelroll 22 which contains a flat steel strip S constructed of steel asdisclosed above and which extends into the series of roller assemblies23, 24, 25, 26, 27, 28, 29, 29A and 29B. These rollers have a shape thatas the strip is passed therethrough the strip of steel is graduallyformed into the form as disclosed in FIG. 3. Although I have disclosednine such roller assemblies for illustration purposes only, the numbercan be substantially increased and for some shapes may actually bedecreased. Near the end of the apparatus 20 is the induction welder 30of any well known type that will weld the two edges 31 and 32 togetherafter such edges are caused to abut each other as disclosed in FIG. 9.In welding the abutting edges the induction welder 30 generatessubstantial local heat in the area of the tube near the weld whichassists in the sweeping of the tube as will now be described.

A unique means is provided downstream of the induction welder 30 forproducing the sweep (sweeping) of the bumper bar 1 as disclosed in FIG.2. This sweep producing or sweeping means disclosed in FIGS. 4, 10 and11, comprises a sweeping box 33 which includes a series of pairs ofinternal and external mandrels (34a and 35a, 34b and 35b, etc.) betweenwhich the tube formed by the rollers 23-29b and induction welder 30pass. These mandrels have rounded ends as disclosed to assist in guidingthe tube 1 between them. Each external mandrel is held by a mandrelframe such as 36a (FIG. 11) which is anchored at a horizontalcenterpoint by a stabilizer 37a. The sweep of the tube may be increasedby vertical adjustments of the sweep adjusters 38a, 38b, 38c, etc. Forexample, as sweep adjuster 38a is adjusted upward, stabilizer 37a isalso raised, thus forcing mandrel frame 36a and external mandrel 35aupward. Obviously, internal mandrel 34a is forced to follow thismovement since the cross-sectional shape of the internal mandrels 34a,34b, etc. are substantially identical to the cross section of thebumper 1. Therefore, as the roller formed tube passes thereover, itassumes the curvature or sweep of the mandrels.

The internal mandrels are supported by a support assembly 40 (FIG. 6)which includes two rods 41 and 42 extending from and secured to thesupport 43. The location of support 43 is selected to a position wherethe support 43 can extend downwardly into the tube as illustrated byFIG. 6. At this position, the steel strip has been rolled to form thefront side 2 and the two top and bottom sides 4 and 5 and wherein theback side has not yet been formed leaving an opening 14 through whichthe support 43 extends.

It should be understood as the steel strip continues to pass through therollers 27, 28 and 29 downstream of the support 40, it is progressivelyformed by the rollers 27, 28 and 29 to the shape as disclosed in FIG. 8.FIG. 9 discloses the shape of the tube roller formed to the desiredshape with the edges 31 and 32 abutting. As the tube thus formed passesthrough the induction welder 30, the edges 31 and 32 are weldedtogether. The tube then continues through rollers 29a and 29b which pushagainst an internal mandrel 29c (FIGS. 9 and 12) which is similar inshape to the inside cross section of bumper bar 1 (FIG. 9). This allowsrollers 29a and 29b to generate sufficient force to force bumper bar 1forward across the sweeping box 33 without crushing or deforming thecross section of bumper bar 1.

As previously referred to, the indentation in the front side 2 of thebumper bar 1 is provided for two reasons. It gives additional strengthto the bumper 1 and also provides a means for moving the bumper tubeover the mandrels 34, 35 and 36. As illustrated in FIG. 9, theindentation 6 includes the ledges 7 and 8 which are engaged by theprojecting sides 45 and 46 extending radially outwardly from roller 29b.Also, indentation 10 includes ledges 11 and 12 engaged by projectingsides 47 and 48 extending radially outwardly from rollers 29b. Thisengagement between the edges formed by ledge 7 and side 45, ledge 8 andside 46, ledge 11 and side 47 and ledge 12 and side 48 of the rollerassembly 29b, and any of the other roller assemblies upstream thereofwherein the indentations 6 and 10 have already been formed, drives oradvances the bumper bar 1 over the mandrels 34 and 35 in sweep box 33.This driving force also is created by roller 29a.

As disclosed in FIG. 4 a cutoff apparatus 50 is disclosed downstream ofthe mandrels 34 and 35 for cutting off the bumper bar 1 at its properlength. The bumper bar 1 that has thus been cut off is ready for furtheroperations such as providing an attachment means for attaching thebumper bar 1 to the vehicle.

OPERATION

Having described the apparatus 20 and the bumper bar 1 that is formedthereby, the operation of the apparatus 20 and the uniqueness of thebumper bar 1 is evident. The steel strip S payed off from the roll 22passes through the roll assemblies to form the tube as disclosed in FIG.9 with the edges 31 and 32 of the steel strip abutting each other. Theinduction welder 30 forms the welded seam 13 to form a unitary integraltube 13 as disclosed in FIG. 10, the tube thus formed being straight.

It is within the contemplation of the broader aspects of this inventionthat the tube thus formed can be utilized as a straight bumper barhaving substantial improved characteristics. It has a substantiallyhigher level of strength and damage resistance so as to meet consumerexpectation and government regulation concerning low speed vehicularimpact. It has also low weight to minimize vehicular dead weight and lowmanufacturing costs. The high strength-to-weight ratio and ease ofmanufacture contribute to the superiority of the present bumper. Suchsuperiority is made possible by forming the bumper of a high-strengthsheet steel, with lower than normal thickness, roll-formed as disclosedabove.

In accordance with the preferred more narrow aspects of this invention,the tube formed by the roller assemblies 23-29 and welder 30 is curvedor sweeped to produce a bumper having a sweep of from 0-60. The higherthe sweep, the stronger the bumper and the more spring back of thebumper. Such curvature or sweep is produced by passing the tube from theinduction welder over the curved mandrel pairs 34a, 34b, etc. and 35a,and 35b, etc. it being understood that one or more mandrels can be used.The tube is passed over the mandrels immediately after the weld seam 13is produced by the induction welder 30. Thus, the steel is still in alocally heated condition which assists in the ease of curving orsweeping the tube without adversely affecting the structure. After thesweep is formed, the bumper bar 1 is cut off by the cut off apparatus 50(FIG. 4).

The sweeping of the tube after it leaves the welder 30 is made possibleby the unique support assembly 40 (FIGS. 6 and 7) located upstream ofseveral of the roller assemblies so that the support 43 can extendthrough the opening 14 and into the tube so as to support the mandrelsdownstream by means of the rods 41 and 42.

The driving of bumper bar 1 through the sweeping box 33 as is madepossible by the rollers 29a and 29b and indentations 6 and 10, theconfigurations of which generate sufficient force to force bumper bar 1through sweeping box 33.

MODIFICATION

The present roll-formed bumper as described above makes possible a novelmeans for supporting the bumper on the vehicle. FIGS. 13 and 14 disclosesuch means which includes the ends of the bumper 1 being crushed anddeformed to provide a flat surface 51 to which securement means such asbolt 52 (FIG. 13 can be attached for mounting the bumper bar 1 to a flatsurface on a support such as a bracket 53 extending from the vehicle.

More specifically, as disclosed in FIGS. 13, 14 and 15, flat surface 51and its orientation with respect to support bracket 53 is provided bythe crushed or deformed outer ends of the bumper. As best disclosed inFIG. 15, rear side 3 is inclined to front side 2 thereby causing thecollapsed portions 4a and 5a of sides 4 and 5. Collapsed side portions4a and 5a provide the inclined flat surface 51 with a predeterminedorientation allowing the surface 51 with a predetermined orientationallowing the surface 51 located on the plane P--P (FIG. 14) to mateablybutt against a bracket 53 extending from a vehicle. A hole is providedat each end (only one end is shown). Hole 54 extends through the frontside 2, rear side 3 and surface 51 and receives attachment bolt 52. Thedeformed end of bumper 1 and bolt 52 thereby form a structure forattachment of bumper bar 1 to a part of the vehicle such as bracket 53.

Although I have disclosed a preferred embodiment of this invention, itshould be understood that many variations could be made withoutdeparting from the spirit and scope of the novel concepts of thisinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows.
 1. An apparatus for makingbumpers comprising:a first roller means for roll-forming a sheet of hightensile strength steel having side edges to cause said side edges toabut one another; means for welding said side edges together to form anintegral tube; a means for forming a sweep in said integral tube; saidfirst roller means being adapted to form at least one irregular surfacein said tube; second roller means downstream of said first roller meansand upstream of said means for forming a sweep; said second roller meansshaped to extend into and engage at least portions of said irregularsurface in the tube; and said shape of said second rollers by engagingat least portions of said irregular surface being adapted to advance thetube in the means for forming a sweep.
 2. An apparatus for makingbumpers comprising:a first roller means for roll-forming a sheet of hightensile strength steel having side edges to cause said side edges toabut one another; a means for welding said sides edges together to forman internal tube; a means for forming a sweep in said integral tube;elongated support means extending a distance upstream of the weldingmeans to a predetermined position wherein said side edges are spaced onefrom the other; said elongated support means supporting said means forforming a sweep in said integral tube; an anchoring structure supportingsaid elongated support means at said position; said first roller meansbeing located upstream of said means for forming said sweep and shapedto form an irregular surface in the tube; and a second roller meanslocated downstream of said first roller means and shaped to engage atleast portions of said irregular surface to thereby advance the tubeinto the means for forming a sweep.
 3. An apparatus for making bumperscomprising:a first roller means for roll-forming a sheet of high tensilestrength steel having side edges to cause said side edges to abut oneanother; a means for welding said side edges together to form anintegral tube; a means for forming a sweep in said integral tube; saidmeans for welding being an induction welder located upstream of saidmeans for forming a sweep in said integral tube, said induction weldergenerating heat in the tube which assists the sweep forming means informing said sweep; said first rollers being located upstream of saidmeans for forming a sweep and shaped to form an irregular surface in thetube; and a second roller means shaped for engaging at least portions ofsaid irregular surface to thereby advance the tube into the means forforming a sweep.
 4. The apparatus of claim 3 in which the means forforming a sweep includes a mandrel means over which said tube passes. 5.The apparatus of claim 4 in which the mandrel means includes a series ofshort mandrels spaced but connected together.
 6. An apparatus for makingbumpers comprising:a roller means for roll-forming a sheet of hightensile strength steel having side edges to cause said side edges toabut one another; a means for welding said side edges together to forman integral tube; a means for forming a sweep in said integral tube;said means for forming a sweep including a mandrel means attached to bereceived within a tube formed by said roller means; an elongated supportmeans adapted to extend inside a tube, formed by said roller means, adistance upstream of the welding means to a predetermined positionwherein said side edges are spaced one from the other; said elongatedsupport means supporting said mandrel means in said integral tube; ananchoring structure supporting said elongated support means at saidposition; said mandrel means including a series of short mandrels spacedbut connected together.
 7. Apparatus for forming a bumper bar for avehicle comprising roller means for continuously roll-forming a sheet ofhigh tensile strength steel having side edges to cause the side edges toabut one another;means for welding said side edges together to form anintegral tube; sweep forming means for providing a sweep, said sweepforming means having curvilinear external mandrel means and curvilinearinternal mandrel means; support means for supporting said internal andexternal mandrel means in relatively stationary spaced relationship onefrom the other to provide a passageway therebetween for receiving saidintegral tube therebetween, said support means including an elongatedmember attached to the internal mandrel means and extending therefrom toa support member extending through an opening located upstream of saidsweep forming means where the side edges of said sheet are not abutting;means for causing said integral tube to pass through said passagewaywhile said roll-forming of said sheet upstream of said external andinternal mandrel means takes place and said upstream sheet connected tothe integral tube is being roll-formed; said internal and externalmandrel means adapted when said tube is passed through said passagewayto produce a predetermined sweep in said tube as determined by the shapeof said passageway; and cutting means located downstream of said sweepforming means for cutting said swept integral tube at predeterminedlengths whereby a series of bumper bars can be continuously formed insuccession during the roll-forming of said sheet upstream of said sweepforming means.
 8. The apparatus of claim 7 in which the internal mandrelmeans and external mandrel means include a series of short mandrelsspaced from each other but connected together.
 9. The apparatus of claim8 in which inner mandrel means is located at the second roller meanswhereby the tube is clamped between the second roller means and astraight portion of the inner mandrel means for forcing the tube throughthe sweep forming means.
 10. The apparatus of claim 7 in which a firstroller means is provided for forming said tube and a second roller meansis provided for gripping said tube and forcing it through said sweepforming means.
 11. The apparatus of claim 10 in which inner mandrelmeans is located at the second roller means whereby the tube is clampedbetween the second roller means and a straight portion of inner mandrelmeans for forcing the tube through the sweep forming means.
 12. Theapparatus of claim 10 in which the first roller means is shaped to format least one irregular surface in said tube and said second roller meansis shaped to extend into and engage at least portions of said irregularsurface, said shape of said second rollers engaging at least portions ofsaid irregular surface to advance the tube in the means for forming asweep.
 13. The apparatus of claim 12 in which inner mandrel means islocated at the second roller means whereby the tube is clamped betweenthe second roller means and a straight portion of the inner mandrelmeans for forcing the tube through the sweep forming means.